Electric field sensing refers to a method for determining positions, movements and geometries of objects on the basis of disturbances which they cause to a surrounding electric field.
Most of the pioneering work in electric field sensing can be attributed to nature. Electric fields are, used by various aquatic animals for sensing their environment, especially in the dark, muddy waters where light is scarce (Bastian J., Electrosensory Organism, Physics Today, pages 30-37, February 1994).
Professor Neil Gershenfeld's group at the MIT Media Laboratory has applied electric field sensing for measurements of position, shape and size since the early 1990's. Prof. Gershenfeld's group has, for example, developed an interface for human-computer interaction based on electric field sensing and charge source tomography.
In the University of Queensland there has also been studied electric field sensing. A low frequency electric field is generated in order to induce a current and the induced current is measured at receiving nodes. When an object interferes with the electric field, the capacitance of the environment is altered and the received current values are changed. By modeling the effect of a foreign body in the field, the characteristics of this body can be derived by the current values obtained (O'Brien Christopher John, Electric Field Sensors for Non Contact Graphical Interfaces, Thesis, School of information technology and Electrical Engineering, University of Queensland, 2001.).
A critical component of any intelligent environment is a user interface. All user interfaces, such as keyboard, mouse, touchpad and touch screen, have their pros and cons. Most of the user interface devices are typically relatively fragile and expensive, have limited scalability for large areas, and are poorly applicable for use outdoors or in harsh environments. Charge source tomography (CST) is a method for sensing an interaction between a user and flat or curved surfaces which are made sensitive by an addition of a conformable resistive sheet that is able to create electric fields. The CST-based user interface device comprises a resistive sheet, peripheral electrodes, and a current/voltage controller. During operation, a controller applies voltage patterns to points on the perimeter of the resistive sheet and measures the currents that arise as a consequence. The user appears in this system as a capacitive load localized to some region of the resistive sheet. (Post E Rehmi, Agarwal Ankur, Pawar Udai, and Gershenfeld Neil, Scalable Interactive Surfaces via Charge Source Tomography, 2nd International Conference on Open Collaborative Design of Sustainable Innovation. Dec. 1-2, 2002, Bangalore, India; Strachan John Paul, Instrumentation and Algorithms for Electrostatic Inverse Problems, Masters Thesis, Massachusetts Institute of Technology, Cambridge, Mass., 2001.)
The CST enables an interactive surface to be used with bare hands without touching. Furthermore, the CST makes it possible to manufacture low-cost and mechanically robust user interface devices that are scalable and easy to embed into a variety of surface materials and shapes.